cdm61093

Hello I have a 1988 Iroc-z 350 TPI. I am having a problem with my car which shows a code 23. And sometimes the car will not idle till I shut it off and restart it. I am wondering what i should have my base timing set at? I live in colorado at an elevation of 5280 feet. Currently I have set my base timing to 10 degrees before top dead center, But after that I installed a Jet Performance Chip. So would that cause any problems such as being too advanced or retarded? The only other modifications this car has are twin 58 mm throttle bodies, 2.5 Inch exhaust with no catalytic converter or mufflers. Thanks